Electrical contact tape



Aug. 5, 1969 H. TY ETAL ELECTRICAL CONTACT TAPE Filed Aug. 10, 1966 FIGI.

2 Sheets-Sheet 1 Aug. 5, 1969 H. TY- ETAL ELECTRICAL CONTACT TAPE Filed Au 10, 1966 F IG 6.

2 Sheets-Sheet 2 FIG] FIGB.

United States Patent 3,459,516 ELECTRICAL CONTACT TAPE Henry Ty and Rene A. Dubuc, Attleboro, Mass., assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Aug. 10, 1966, Ser. No. 571,609 Int. Cl. B21b 15/00, 47/00 US. Cl. 29-191.6 4 Claims ABSTRACT OF THE DISCLOSURE Among the several objects of the invention may be noted the provision of metallic weldable electrical contact tape having a metal facing layer and a metal backing layer to which the facing layer is metallurgically bonded, the backing layer having an improved embossed pattern; the provision of electrical contact tape wherein said pattern is of raised form which admits of being more accurately shaped by knurling; and the provision of such a pattern on the backing layer which under continuous welding operations creates a more uniform weldment all along the tape length. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

FIG. 1 is a plan view of one form of electrical contact tape made according to the invention;

FIG. 2 is an ideal cross section taken on line 22 of FIG. 1;

FIG. 3 is a plan view like FIG. 1 illustrating another form of the invention;

FIG. 4 is an ideal cross section taken on line 44 of FIG. 3;

FIG. 5 is a view illustrating a pair of forming rolls for producing the tape of the invention by knurling;

FIG. 6 is a view showing one step in a useful application of one form of the new tape;

FIG. 7 is a view similar to FIG. 6 showing certain perforations from which certain switch arms have been cut;

FIG. 8 is a side view of a switch arm as cut from the material of FIG. 7; and

FIG. 9 is a view illustrating a use of the form of the invention shown in FIGS. 3 and 4.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

It is known to provide weldable electrical contact tapes, contacts and the like in which a precious metal facing layer and a base metal backing layer are metallurgically bonded, the backing layer having a raised pattern of projections for facilitating weldment to metal parts. Various patterns have been proposed for the shapes of the projections to be formed, including angled and chevron-shaped ridges, pointed pyramidal projections and others, none of which were entirely satisfactory for making weldable tape made by knurling in the pattern. By

Patented Aug. 5, 1969 the use of prior rolled-in patterns on weldable tape it was difficult to force metal by cold metal fiow so as completely to fill the prior recessed shapes of the female portions of the knurling rolls or dies. This caused irregularities of projections on the finished tape and irregularities of weldment when the tape was welded to supporting parts. By means of the present invention an embossed pattern is obtained by knurling such that the depressed female knurling roll or die parts will be accurately infilled by cold flow of metal so as to produce more evenly formed projections 0n the finished tape. As a result there is obtained a more accurately formed electrical contact tape which may be more strongly, evenly and reliably welded at all points along its length.

Referring now more particularly to FIGS. 1 and 2, these show one form of the finished tape made according to the invention. Numeral 1 indicates a weldable metal backing strip which may be composed of a base metal such as stainless steel, nickel, cuprous-nickel such as Monel, or the like. This layer may for example be on the order of 10 mils thick.

On one side of the base strip is a metallurgically bonded layer 9 having a transversely crowned face 11. The metallurgical bonding may be accomplished by solid-phase roll bonding, solder bonding or like known processes. The central thickness of crowned layer 9 may be on the order of 22 mils. The layer 9 may be composed of one of the precious metals such as gold, silver, platinum, alloys thereof and the like, generally useful as electrical contact material.

Pressed or embossed into the other face of backing layer 1 by knurling are upwardly tapering projections 3 which are in the form of low truncated pyramide, as indicated at 5. The truncations 5 are substantially flat and lie substantially in a common plane. This is a feature of importance as regards the improved weldability of the finished tape. The bases of the projections 3 are preferably of whole or partial diamond shapes as illustrated. They are positioned in angular rows so as to provide shallow grooves 7 between them which are on a bias relative to the length of the tape. The angular arrangement of the projections favors their formation by knurling. The depth of the grooves 7 and height of the truncated pyramids 3 may for example be on the order of 4 mils.

A typical set of pressure rolls for knurling is illustrated at 13 and 15 in FIG. 5. Roll 15 contains a groove 17 for the reception of a flange 19 on roll 13. This flange 19 is provided with knurling 21 in the form of shallow female recesses 20 which by cold flow form the desired male contours of projections 3. The hollow recesses are of whole or partial diamond shape with inwardly sloping sides. The initially unknurled metallurgically bonded composite strip 1, 9 is fed between the rolls 13 and 15 with the backing layer 1 against the knurling flange 19. The shallow bottoms of the recesses in the flange 19 permit of reliable and complete infilling by cold flow of the material of the backing strip 1 to produce the projections 3, 5 in accurately coplanar fiat-topped truncated form. This distinguishes from former shapes of projections which terminate in points or knife-like edges which required their converse forms in the female depressions of the knurling roll. The converse forms were diflicult to infill accurately by cold fiow with resulting inaccuracies in the heights of the corresponding pointed or knife-edged projections on the finished tape.

Referring nows to FIGS. 3 and 4 there is shown a modified form of the invention in which like numerals designate like parts. In this case the base metal backing strip is numbered 2 and the precious metal facing strip is numbered 10. The strip 10 in this case is flat and the low truncated pyramidal projections 3, 5 do not extend entirely across the strip, unknurled margins 23 being left. In this form of the invention the thickness of the base metal backing strip is, for example, on the order of 8 mils and that of the precious metal facing strip 10 is on the order of 1 mil. The depth of the grooves between the projections 3, which determines the heights of the latter, is on the order of 3 mils.

Referring now to FIGS. 6-8 there is illustrated use of the electrical contact tape of FIGS 1 and 2. In FIG. 6 is illustrated a strip 25 to which the tape such as shown in FIGS. 1 and 2 has been welded by conventional continuous seam-welding apparatus (not shown). This welding apparatus progressively presses the tape with its truncations against the strip 25 as welding current flows through the truncations to form a welded connection all along the tape. By punched perforations 27, shown in FIG. 7, switch arms such as shown at 29 in FIG. 8 may be produced having an endwise contact 31 formed by the segmented portions of the welded strip. As will be readily understood several tapes may be applied to one or both sides of strip 25 to provide additional contacts on switch arms such as 29.

In FIG. 9 is shown a product upon which are contacts 33. These are constituted by portions of a pre-applied electrical contact tape constructed as in FIG. 4. In this case the end product is in the form of an electrical contact clip 35. This originally was part of a fiat sheet of metal to which tapes made according to FIGS 3 and 4 were continuously seam-welded. The sheet was then segmented and the segments bent to the form shown in FIG. 9, upon which welded tape segments 33 remain as contacts.

An advantage of the invention is, first, that the accurately formed low truncated pyramidal projections afford means for reliably obtaining by knurling accurately shaped coplanar areas such as 5 for engagement to surfaces to which the electrical contact tape or parts thereof are to be applied. As a result, uniformity of weldment of all projections is obtained under continuous welding conditions. Moreover, by the use of the shallow flat truncations of the invention such as 5, the flow of current during a welding cycle is more nearly constant. Better weldability at all points through the length of the tape minimizes the occurrence of faulty contact parts.

In the following claims, the phrase general diamond shape means in the shape of a rhombus or a part of the same, as illustrated in FIGS. 1 and 3.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Composite electrical contact tape comprising a base metal backing strip metallurgically bonded on one side with a precious metal facing strip, said backing strip being provided on its other side with projections, each of which has a truncated tapered form.

2. Composite electrical contact tape made according to claim .1, wherein each truncated tapered form is in the form of a pyramid having a substantially flat top area lying substantially in the plane of the other flat top areas of the projections.

3. Composite electrical contact tape made according to claim 2, wherein the projections are of general diamond shape and arranged to provide grooves between them disposed on a bias relative to the length of the tape.

4. Composite electrical contact tape made according to claim 3, wherein the total thickness of the composite is on the order of mils or less and depths of the grooves and heights of the projections are not over approximately 10 mils.

References Cited UNITED STATES PATENTS 328,652 10/1885 Claude 29-193.5 1,907,931 5/1933 Henderson 219-93 2,624,820 1/ 1953 Payette 29-191 3,118,049 1/1964 Gros et al. 219-93 3,346,350 10/ 1967 Spooner 29-191.6

L. DEWAYNE RUTLEDGE, Primary Examiner E. L. WEISE, Assistant Examiner U.S. Cl. X.R. 29-193 

